fix(ast_tools): oxc_ast_tools depend on local oxc_* crates (#15565)

Fix #15564.

`oxc_ast_tools` depends on Oxc crates from crates.io, not the local workspace. When AST changes break local crates, the codegen can't compile either - a Catch-22 situation, since running codegen is the only way to fix compilation.

This isn't ideal as it complicates dependency management. Alter `oxc_ast_tools` so it depends on crates from local workspace, and work around the Catch-22 problem by introducing a `generate-js` Cargo feature which disables these dependencies, so the codegen can still compile if they're broken.

## Changes

- **Add `generate-js` Cargo feature** (enabled by default)
  - Makes all `oxc_*` dependencies optional, activated only when feature enabled.
  - Only JS generators (`RawTransferGenerator`, `TypescriptGenerator`, `ESTreeVisitGenerator`, `RawTransferLazyGenerator`) require these dependencies.

- **Conditional compilation**
  - Gate JS generator modules and `Output::Javascript` variant behind `#[cfg(feature = "generate-js")]`

- **Fallback in `just ast`**
  ```sh
  cargo run -p oxc_ast_tools || (
    cargo run -p oxc_ast_tools --no-default-features
    && cargo run -p oxc_ast_tools
  )
  ```
  First attempts to run full codegen. On failure, regenerates Rust code only, without dependencies (so that `oxc_*` crates will now compile), then retries full generation.

Author: Copilot